I see it as if you write a song for a band that you currently play in, then that song belongs to the band, regardless of who leaves, even if it is the person who wrote it. That's how I've always worked anyway

I do understand however that anything one writes for a band is like cutting off a chunk of your own flesh just so the rest of the band can mutilate it into submission, but each to their own I guess.

When Pink Floyd "broke up" (Roger Waters left), the rest of the band continued touring using Waters' songs. He tried to sue them, but was unsuccessful. Waters even tried to sue them for rights to the band name 'Pink Floyd', but was, again, unsuccessful.

Moral: Be careful who you share your material with. In the case of Pink Floyd, a large band with lots of fame and business and legal ties, Waters was not able to reclaim the property that he mostly wrote. In the case of the more typical, smaller bands, you're still likely gonna be screwed because there will be no legal precedence.